Mr. Billington wrote six books on Russia and revolutionary traditions. His “Mikhailovsky and Russian Populism” (1958) was the first major biography of the 19th-century Russian social critic Nikolai Mikhailovsky. In “The Icon and the Axe: An Interpretive History of Russian Culture” (1966), he examined 1,000 years of intellectual life in Russia. Leonard Shapiro, in The New York Review of Books, called it a “magisterial survey of the past.”

Vice President Pence and Russian President Vladimir Putin sat next to each other and chatted briefly Thursday at the East Asia Summit in Singapore, in a conversation that also included national security adviser John Bolton.

With Roy Medvedev, the physicist Andrei D. Sakharov, the author Aleksandr I. Solzhenitsyn and others, Dr. Medvedev was a central figure in the seething intellectual dissidence that exposed, largely through underground literature known as samizdat, the repression of ideas, science and human rights in the Soviet Union.

Senate Foreign Relations Chairman Bob Corker, who would be key to advancing any legislation, said that passing a bill he’s sponsored called the Deter Act “would be sort of missing the mark” after a U.S. vote that appears to have been unmarred by Russian meddling.

Russia hosted a group of Afghan government-linked envoys along with their Taliban rivals Friday, as the Kremlin waded into efforts to end a 17-year conflict where Western efforts have repeatedly failed.